Current status and performance goals for serum thyroglobulin assays.

Serum thyroglobulin (Tg) measurements are used as a tumor marker for monitoring patients with differentiated thyroid carcinoma. The clinical utility of six different Tg methods [RIA or immunometric assay (IMA)] currently used in Europe and the US was evaluated, with focus on methodologic standardization, sensitivity, interassay precision across the typical clinical monitoring interval (6 to 12 months), "hook" effects (IMA methods), and Tg autoantibody interference. The methods evaluated were: DYNOtest Tg (Henning), OptiQuant Tg (Kronus), SELco Tg (Medipan), Thyroglobulin IRMA (Pasteur), Nichols Chemiluminescent ICMA (Corning Nichols), and an RIA developed by us (USC Endocrine Services Laboratory). The clinical impact of the current methodologic problems on the use of serum Tg measurements is reviewed. Optimal performance goals are recommended for manufacturers developing and laboratories and physicians selecting a serum Tg method to use for serial long-term monitoring of thyroid cancer patients.